Python implementation of the Wilson Score Interval?

Question

After reading How Not to Sort by Average Rating, I was curious if anyone has a Python implementation of a Lower bound of Wilson score confidence interval for a Bernoulli paramet

Answer 1

The accepted solution seems to use a hard-coded z-value (best for performance).

In the event that you wanted a direct python equivalent of the ruby formula from the blogpost with a dynamic z-value (based on the confidence interval):

import math

import scipy.stats as st


def ci_lower_bound(pos, n, confidence):
    if n == 0:
        return 0
    z = st.norm.ppf(1 - (1 - confidence) / 2)
    phat = 1.0 * pos / n
    return (phat + z * z / (2 * n) - z * math.sqrt((phat * (1 - phat) + z * z / (4 * n)) / n)) / (1 + z * z / n)